Intense ultrasonic fields are used for treating materials in various ways including cleaning surfaces, promoting certain types of chemical reactions, and degassing liquids. Such fields are generally generated by electrically driven piezoelectric or magnetostrictive transducers. In general, these transducers produce acoustic waves which include intense compression pulses. For example, U.S. Pat. No. 5,164,094 Stuckart; U.S. Pat. No. 4,673,512 Schram; U.S. Pat. No. 4,983,189 Peterson et al.; and U.S. Pat. No. 5,192,450 Heyman disclose prior art acoustic liquid processing devices. Other prior art acoustic liquid processing devices include U.S. Pat. No. 2,578,505 Carlin; U.S. Pat. No. 3,056,589 Daniel; U.S. Pat. No. 3,021,120 Van der Burgt; U.S. Pat. No. 3,464,672 Massa; U.S. Pat. No. 4,369,100 Sawyer; U.S. Pat. No. 4,433,916 Hall; U.S. Pat. No. 4,352,570 Firth; U.S. Pat. No. 3,946,829 Mori et al.; European Patent specification 0 449 008 Desborough; and Japanese patent 3-151084 Murata.
McCord, U.S. Pat. No. 4,618,263 discloses an acoustic cleaner which incorporates a cavitation generator for agitating liquid in an enclosure. The enclosure is provided with a wave reflecting surface for reflecting acoustic waves from the margin of the liquid back into the body of the liquid to reinforce cavitation in the chamber.
Kanazawa, U.S. Pat. No. 4,727,734 discloses an ultrasonic clothes washer. The washer has a metal tub for receiving clothes. Bubbles are introduced into the tub to promote cavitation and to reflect the ultrasound so that all articles in the tub are irradiated with ultrasound.
A disadvantage of prior art cavitation chambers is that the electromechanical equipment for generating high powered acoustic signals with a piezoelectric or magnetostrictive transducer is inherently expensive and inefficient. Another disadvantage of such apparatus for liquid degassing purposes is that the intense high pressure pulses can interfere with the degassing process.